12:55 PM, Thursday, May 7, 2015
A cool, moist pattern will continue into Sunday for the whole Front Range region. A large, wet storm system is likely to move slowly through the region Friday night to Sunday morning. At this point I am confident that the weekend storm will be major (2-3″ liquid equivalent) for eastern Wyoming and western Nebraska including Cheyenne and Laramie. I am also confident that southern Colorado will likely be south of the heaviest precipitation. I have a lot less confidence about the impacts for northeast Colorado, including Denver-Boulder-Fort Collins. Current indications are for significant precipitation, but less than what is likely immediately to the north. But we will have to watch the development closely.
Thursday evening through Friday: Dry periods, but mostly cloudy with rainy periods too. There may be some heavier showers or thundershowers that trigger minor local flooding in the late afternoon or evening both days. Snow levels are likely to stay near tree line. Thunderstorms are a little more likely south of Denver where the sun is poking through.
Friday night through Sunday:
As the storm moves from the Four Corners to eastern Colorado Friday night to early Sunday we can expect a wet period, with snow levels lowering by Saturday night from near treeline to between 6000 and 7000 feet, and possibly all the way down to the plains Sunday morning. Because it appears that the Denver-Boulder area may be south of the heaviest precipitation, snow accumulation, if any, will probably be minor because much of the precipitation will fall as rain. The Front Range foothills have the potential to see 6-12 inches, with more in the higher mountains and passes.There is a small chance that the heavier part of the storm will shift south, so pay attention to the weather before venturing out. Either way, freezing temperatures by Monday morning are likely to damage unprotected annuals.
For southeastern Wyoming and the northern parts of Larimer and Weld counties in Colorado, heavier amounts are probably, with a couple feet of snow from Rocky Mountain Park north into the Medicine Bows and the Laramie Range. Even Cheyenne has a good chance for getting more than 6 inches of snow after a couple inches of rain. Be prepared for rough driving along I-80 and I-25 north of Fort Collins.
Colorado Springs and south:
Unsettled here too, but less chance that the weekend storm will be really big. But watch out for a few heavy thunderstorms today and Friday.